The invention relates to a dental composition comprising
(a) 10-99.999% by weight of a functional acrylic-acid and/or methacrylic-acid ester dental compound, PA1 (b) 0.001 to 5% by weight of an initiator system capable of initiating radical polymerization, and PA1 (c) 0 to 89.999% by weight of auxiliary agents, such as fillers, thixotropic agents and the like, wherein the % by weight is based on the total weight of (a)+(b)+(c). PA1 (a) 10-99.999% by weight of at least a bifunctional, or polyfunctional, e.g., trifunctional, acrylic-acid and/or methacrylic-acid ester dental compound, PA1 (b) 0.001 to 5% by weight of an initiator system capable of initiating radical polymerization, and PA1 (c) 0 to 89.999% by weight of auxiliary agents, such as fillers, thixotropic agents and the like, wherein the % by weight is based on the total weight of (a)+(b)+(c), and PA1 (d) 0.001 to 10% by weight, based on the weight % of (a), of a dental compound of the general formula ##STR3## in which: Ar represents aryl or substituted aryl, which is substituted by straight-chain or branched-chain C.sub.1-18 alkyl, C.sub.1-18 -alkoxyl, carboxyl-C.sub.1-17 -alkyl or halogen, PA1 R.sup.1, R.sup.2 and R.sup.3, which are the same or different, represent hydrogen, aryl or substituted aryl, which is substituted by straight-chain or branched-chain C.sub.1-18 -alkyl, C.sub.1-18 -alkoxyl, carboxyl-C.sub.1-17 -alkyl or halogen, or represent a straight-chain or branched-chain C.sub.1-18 -alkyl, C.sub.1-18 -alkoxyl, or C.sub.1-17 -alkoxycarbonyl, in which alkyl and alkoxyl can be substituted by halogen or aryl, PA1 in which, R.sup.1 or R.sup.2, when represented by aryl or substituted aryl, which is substituted by straight-chain or branched-chain C.sub.1-18 -alkyl, C.sub.1-18 -alkoxyl, carboxyl-C.sub.1-17 -alkyl or halogen, or when represented by C.sub.1-18 -alkyl or C.sub.1-18 -alkoxyl, can be linked with Ar by a single bond and PA1 in which, Ar, when represented by phenyl, C.sub.1-18- -alkylphenyl, C.sub.1-18 alkoxyphenyl, carboxyl-C.sub.1-17 -alkylphenyl or halophenyl, R.sup.2 can be represented by --O--, which is linked with the phenyl or phenyl moiety of Ar to a benzofuran and PA1 in which, at least one of R.sup.1 to R.sup.2 represents H and at least one of R.sup.1 to R.sup.2 represents aryl or aryl substituted by straight-chain or branched-chain C.sub.1-18 -alkyl, C.sub.1-18 -alkoxyl, carboxyl-C.sub.1-17 -alkyl or halogen. PA1 1. With the photopolymerizable dental compositions according to the invention, through the use of component (d), the polymerization to hard polymers are no longer suddenly formed within a few seconds (10-20 seconds), but instead the polymerization proceeds evenly over a period of 20 to 60 seconds and as a result, stresses which could occur inside the polymers can be avoided. If the dental composition according to the invention is exposed to light for only a short period of time (10-30 sec.), the material is still readily workable mechanically and can be further hardened in subsequent stages of light-exposure. With tooth-filling materials, in particular, better results are obtained in tooth-fillings with respect to marginal fissures and adhesion to the surrounding tooth material. The occurrence of micro-cracks from stresses is also reduced and as a result the abrasion resistance of the material is improved. A further advantage is that due to the slow setting only a moderate temperature increase occurs due to the reaction heat liberated during the polymerization. PA1 2. With the redox-polymerized dental compounds of the dental composition according to the invention, in addition to the aforementioned advantages one obtains a good workability of the compounds after the polymerization has begun, i.e. the rubber-elastic transition state is maintained for longer and thus any surplus can still be readily removed during the cementing and positioning of a filling. PA1 3. The dental compositions according to the invention have a particular advantage when used as temporary crown and bridge material. Because of the longer rubber-elastic setting phase it is possible for the dentist to remove the temporary structure from the mouth of the patient when it is not yet in a completely hardened state and to perform work thereon without endangering its dimensional stability. In contrast to previous materials, a period of several minutes is available for the removal of the temporary structure, so that even temperature influences, the size of the temporary structure and the storage of the materials, have little effect on its processibility.
Dental compositions containing polymerizable dental compounds, e.g. tooth-filling materials, temporary crown and bridge materials or cementing materials, consist of plastics which are provided with organic or inorganic fillers. Depending on the intended application these can be highly liquid to highly viscous compositions. Temporary crown and bridge materials, for example, must on one hand show a good rheology so that they flow throughout the mold in question, on the other hand they must not be so fluid that they would flow out of the mold during a fitting in the jaw. These temporary crown and bridge materials are usually systems having a relatively low amount of fillers, which contain approximately 10 to 70% by weight of inorganic filler. The fillers used generally have an average particle size of 1 to 15 .mu.m. In addition, considerably finer fillers having a particle size of from 0.02 to 0.05 .mu.m are also used with the above fillers to make the compounds sufficiently plastic and thixotropic. The use of organic fillers, such as polymethacrylate, has also proved useful as temporary crown and bridge materials.
When producing such dental composition the object in the past has always been to not only allow the dentist sufficient time for processing, but also to keep the setting phase (that is the amount of time from the start of gelation to the time at which the hardening of the composition is complete), as short as possible, thus keeping the time in which a patient is being treated to a minimum. To achieve this objective, it was necessary to use systems which were as reactive as possible, such systems as photoinitiators or redox catalysts, which initiate the radical polymerization of acrylic-acid and methacrylic-acid esters in a short period of time. For example, European Patent Application 0 059 451 describes the use of certain malonyl sulphamides as activators for the peroxidic polymerization of polymerizable dental compounds. One of the advantages mentioned therein is the short setting phase despite the long processing time. In a similar manner the German laid open print 14 95 520 describes a process for the polymerization of acrylic-acid esters in which a catalyst system, consisting of organic peroxide, ionogenic halogen, a copper compound and a barbituric acid is used as the activator.
Even when photoinitiators were used the object was to employ the most reactive possible systems for the polymerizable dental compounds. This made possible a rapid polymerization in the short irradiation phase. For example, European Patent Specification 1 84 095 describes particularly reactive bis-acylphosphine oxides as photoinitiators for dental compounds.
The use of the most reactive possible initiator systems for the polymerization of the dental compounds based on acrylic-acid or methacrylic-acid esters has admittedly brought the advantage that hard plastic materials can be obtained in very short periods of time, for the dentist. However, because of the extremely rapid setting phase the problem arose that for some applications the time for preparing and processing the dental materials was too short, particularly for removing temporary crown and bridge materials.
Adhesive compositions are known from European Patent Application 211 104 which contain vinyl compounds and a compound of the general formula ##STR2## in which R.sub.1 represents hydrogen or methyl and R.sub.2 represents hydrogen or an optionally substituted alkyl radical with 1 to 5 carbon atoms. Bifunctional methacrylic-acid esters are mentioned among others as the vinyl compounds. Moreover, hardened resins and their use for the production of optical lenses are known from the German laid open print 31 20 965, which have been manufactured from bifunctional acrylic-acid or methacrylic-acid esters and a further unsaturated compound, in which the further unsaturated compound can be styrene, alpha-(C.sub.1-3)-alkylstyrene, vinyl naphthalene, etc. Tests have however shown that unsaturated compounds with only one aromatic radical such as described in the two above publications do not have a satisfactory effect with regard to the lengthening of the setting phase. Such additives are in any case only effective in very high concentrations and even then not to a satisfactory degree. It could therefore be established that the alpha-methylstyrene mentioned by way of example in the above published application is unable to effect any useful lengthening of the setting phase. Moreover, this type of compound has problems with regard to storage-stability and processing due to its low volatility, and in many areas of application, e.g., in dental compositions, the addition of readily volatile compounds is undesirable.